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Utility to help sys admins thwart SSH crackers

DenyHosts is a program that automatically blocks SSH
brute-force attacks by adding entries to /etc/hosts.deny.
It will also inform Linux administrators about offending
hosts, attacked users and suspicious logins.

Synchronization with a central server is possible too.

Differently from other software that do same work, denyhosts
doesn't need support for packet filtering or any other kind
of firewall in your kernel.